Your post title is misleading...
You are either mis-understanding the scope of the graphs shown or deliberately trying to draw an impossible conclusion based on the simple premise of manufacturing over time.
This is based as a percentage. 3.3% of several million of 6-pin/8-pin graphics cards vs 4% of thousands or hundreds of thousands or maybe even a million or so 12VHPWR graphics cards DOES NOT mean that there has been more failures of those within a couple of years vs 15+ years of the existing 6+2pin PCIe power connection existing. I'd hazard a guess that more graphics cards that were manufactured with 6+2pin connectors have been scrapped/recycled than 12VHPWR have been manufactured within the last 2 years.
It's also based on survey data, not actual recording of hardware failures/returns or the result of some intermediate party that has some reason to keep statistics on such a thing (e.g. an insurance company, etc.), so it's not exactly an infallible data set.
Using that same percentage against a sample of 100 of each type would mean that maybe 3 of one type and 4 of the other type would have issues. In any case they would need another 20+ years of both types being manufactured equally before they would even be close of approaching a similar number of overall failures.
I'm not defending the 12VHPWR standard - as soon as I saw it and the power limits designed for it I was like "ok... we'll see how that goes" having already seen failures on the existing 6+2pin system which (as GN itself touched upon) has quite an amount of headroom in its design. To be honest, I was surprised to see so many issues straight out of the gate - I expected it to at least be more of a used / second hand market type of issue.
Also, the simple premise of 'make something better than existed before' has certainly not been the case - if anything 12VHPWR has made the argument for the
HPCE + PCIe connector (see link) a much stronger one even if that means backwards compatibility may go out the window or a load of cases with seperate GPU mounts and extension cables need to replacement parts (unless some cards have an auxiliary port).